Experimental Spindle Torque and Open-Water Performance of Two Skewed Controllable-Pitch Propellers

Experimental results are presented on the spindle torque and open-water performance of two skewed controllable-pitch propellers. Both propellers have radial distributions of skew specified so that the section midchord is forward of the spindle axis at the inner radii and aft of the spindle axis at the outer radii. One propeller has no rake and the other has substantial forward rake. The experiments were conducted at steady conditions in uniform flow in a towing basin over a range of positive and negative pitch ratios and a range of positive and negative advance coefficients so that the complete maneuvering envelope of the ship was simulated in a quasi-steady manner. The experimental open-water performance was correlated with calculated values based on a least-squares fit to previous systematic experimental data. The correlation indicates that the calculation procedure may be adequate for preliminary dynamic simulation studies in cases where open-water data are not available on a similar model propeller. The experimental hydrodynamic spindle torque results are generally consistent with previously reported experimental results. These results suggest that realistic highly skewed propellers can be designed with spindle torque characteristics comparable to those of equivalent propellers without significant skew. No definite conclusions could be drawn regarding the effect of forward rake on spindle torque. The experimental values of centrifugal spindle torque generally agreed with analytically calculated values over a range of pitch ratios.